Observations on the parasitism of Isaria farinosa (Dicks.) Fr. with special reference to the larch sawfly (Nematus erichsonii Hartig.) [microform]

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1998

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MIC»OCOfV lESOlU^ION IBT CHAIT

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ObsenratioflfjiMi IIm^ f»l»^r Isaria f<iriiio«i

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Section IV., V.Ut\.

ur, I

TlUN-i T!

] f

VII. — Ohxiriiilionx on Ihf rniiixilisni of Imtrin farimmi ( I lick.; ) /•'(■. nilh
special rrfirtitre to tin Larrk Siiwtli/ (.Vi /;('/^^•^ ntchsniiH llurlij.".

Hy II. T. (iisHow, Ddininion Botanist.

il'oirinninii'alcil \>\ Dr. Wrii. .■<:iiiiiiIit~. r'.lt.SC, :iiii| rv.ni .'Tili S,|.iiiiil,. r. I'llii .

The fun IS on \vlii<-li I wish to roconl :i few o[)scrv!itions i-. as no
(loulit you ;i I- jiwarc. one of tlic coniinDnrst of those fouii.l ;rro\vini: on
insects, at some time or other (hirin;; (HiTereiit stajtes of their (le\elo|)-
nient. Far^'reater importance has lieeri attacheij to these entomoi;enoiis
fiiiiui in recent yi-ars owin^' to their heinn feL'anled as natural factors
in the control of insect pests. 'I'liis i|uesti(iii has intere-teil both IliUo-
iiiojoiiist ami Botanist alike and, owin^r to llie ahirininji increase at the
proeiit (lay of the larcli sawlly on l>otii sides of the .Vtlantic, n special
study of tliis particular fun;;us has been made more opportune. Theif
were .several points of interest on which further research was desired.
Was the fun>;us known to o( i ..ii the larch sawlly cocoons in llunipe
identical with that observed in Canada' This is, however, one of the
minor |)oints at issue. Still more |>romiiienl was tin- ipiestion -llops
this luiu;us attack the liviin; cocooiis, or the ])upatini; larva' or is it
only seciuidary, u'lowin;; saprophytically on the dead cocoons'.' The
third point of interest was to ascertiiin how infection took place.

I.

The first point whs easily settleil. Material i.e. larch sawfly
cocoons collected by Dr. C. (.iordon Hewitt in Canada, showed small
patches of a whitish fungus K^owin^r on the surface. The cocoons weie
kept under suitable condition.s for further study of the futisus. Some
three weeks later the jirowth had become elon;;ated and had taken the
shape of the cl-.aracteristic forked or toiifiued sporophores with whi<-h
the investigator is (piite fiimiliar. These measured from .':> centimeters
in length; their stalks were orangc' coloured at the ba,-<e ami about
two-thirds of the upjier portion was covered with a white farinaceous
mass. On microscopic examination of these filaments the fungus was
identified as belonging to the genus /.«;/•/(/. being the conidial form of
the ascigerous (pyrenoinycetousi fungus C,.A//rc/w )nilit(iri)i. To eslab-
li.sh, however, the identity of the Canadian .species with the i:uropean
one it was thought advisable to make a series of pure cultures. I
succeeded, with the necessary care, in obtaining iiiiniediately a pure
f'ultuie by removing a small portion of the farinaceous mass composed
ot spores by means of a sterilized platinum needle. The spores at that

2-

^,.

.„, Ui<\\\. siKir.TY OK CANAItA

, l,.„s..lv .•oviv.l till- .•«■<■! >tr...MM. TIkw vv.t.. t.;.n».frnr.l I..

a .t.'iilr \»-u\ .li.-l. r(.i.t!iiniMii Stan.hml Nuliifnt (i.'laimf. \Uvr M,
hour- Miiull la.liHlii.n .-..l.mi.'s U'Ciiin.- visihlo to lli.- uiuikUmI .•>■<•

I'lvviou-lv ilir t:.Tmiiiii,i f tl.r r..l..iirloii,. oviil-slmix-.l ("nitliu

w,- ol.-crv.l will, til.- ai.l of tl,.- umros,ui»-. Aflrr 0 lu.urs th.- first
.iirn, nf n,TM,ii,aii.m .MTmir,!. ihr .[".iv MMi.linL' fnrtl. >nu- or two
til,.- iiivc.'li:il l'il..->. S..iti.'lirii.'s til.- ;;.-nniii!.noii aii.l .l.-v.-l..|>m.-ni
,.,,,nit,a..l .m a.T.,..i.t ui th.- tniirl. .-.ilarp-.l s|.lu-ri.ul .rlU pro.lu.-o.l,
.,f tl,.- .l.-v..loi.ii..'tit of .•oiMiMon v.-aM siM.r...; at oth.-r tin..-s th.- u.-rtnmu-
tioi> r.-s..!„l.l.-a more at. oniii.ary l,yi,hoi..y.'.-tou..* fm.tins. Tlu- yrowtiiK
,..,l„„i,-s fonu.'.l l».autiful ol.j.-rts. Kailialii.^' froi.i tl..- c.-i.tral sp..r.-
th,. iivi.li:.' pro.lur..,! cir.'ular ray^ whi.^h uppcar.-d ^ll;:htly iri.liMont
wli.-i.'l.oMiiii: up tlu- .li.-l. aii.l lookit.n at tl..- ...lotiy tl.rou«h th.- nu-.liiit...
\ft.T a f.'W .lav> 111.- .-..irfac- of llu- p(-tri .lisli aii.l of 'slants" iii t.-st-
tiiU- l..-.ai...- iov.-r.-.l with a ,l.-..s.- it.ass of tufty hyi)ha- ot a .•r.-ai.iish
.,, ,,al.- oraii^o tii.K'.-. Small porti..i.s ..f th.-s.- w.-r.- .•ar.-fi.lly ri-i....v.-.l
aiul .•Nai..ii..-.i. Al.uiiciant sp„r.-s ha.l l«-.-t. pr.ul.i.'t-.l in th.- i.u-ai.tim.v
They an- l.on, in Ion- .hains fmn, •-•-11 "ti fin.-ly .Iniwn out (!ask"hap.-a
.i.-riginata whi.h at.- i-roaun-.l f...iu th.- main ..r lat.-ral hran.-h.-s oi
,iu- mvc-iium in ■■\vho,l>' fnm. 2 to 7. Th.-y w.-r.-. l.ow.-v.-r. al.n
.,l,s..rv't-.l sinjilv. Th.- sp-.n-s pro.lu.'.-.i in tlu- .-uitun-s s..w.m1 th.-n.selvos
all around th.- jin.wini: fun-^u- n.a.s.-.< and n.-w ,■,,1...,..-,- w.-r.- ....nstantly
„l,..-rv.-d and watch.-d. Tlu- spor.-s an.l st.-rif:n,ata w.-r.- m.-asur.-d
■ind w.-r.- foun-l idrntical it. .-v.-ry r.-.-p.-.t with thos.- },'rown m pun-
..ultun- in.tn i;urop.-an mat.-rial. The fun«us ..n tlu- Cal.admii .■u<•.)on^
lu-nn- was idt-litifi.-d as Ismin furiiuisit.

II.

Tlu-r.- has l..n>: In-.-n th.- .■on.-.-plion that ls,m,i f,ir„i.,^,i ^-row-
parasiti.allv .m ins,-ct larva- of various kinds. All t.-xtl.ooks of my-
,.„l„.-v a-r.-.- on that p..int. In th.- ahs.-n.-.-, how.-v.-r (at l.-ast I was not
abh- "to disrov.-r anv ivcords), ..f .U-nu.nstratin- .-xp.-rimi-nts, tlu-s.-
stat.-m.-nts did not .-x.lud.- the p..ssil.ility thai tlu- Isnna may o.-.ui
s,M-.,ndarilv. It was ju>t as lik.-ly that it nn-w .saprophyti.-ally o„
.-...•.Hms or larva, that had di.-.l pr.-viously. In v»-w ..f tlu> fart thai
th.- lan-h sawllv was inrr.-asinfi h.-r.- an.l .-Is.-wlu-r.-. it was tl.ou-ih.
advisal.l.- that tlu- [.arasilisn, of tlu- fundus, if su.-h .-xist.-.l, woul.l plav
an imp..rtant roh- in the contn.l of this .-n.-my of tamaracks.

I niu-t thank hi-re mv fri.-nd an.l .-..ll.-agu.-, Dr. H.^witt, for plariuL-
„mt.-rial in form ..f /.s-.(r,.i ...v.-r.-.l lar.h sawfly rot-oons at. my .lisp..sal
Tlu-s.- .ocooiis w.-r.- i.hiCL-d l..f:.-tlu-r with the moss in which they w.-rc
i„,port.-d from I'nfrlan.l into a Hat «lass ,lish. The moss was nu.ist.-.u...
and a well-fitting li.l pr.-s.-rved the in.)islur.- satisfactorily. 'Ihi- <ai;-

I'VUVSIIISM oi is\ui\ I \KI\os\

'•7

wuM kfpt ill tli<- il.'iik iiinli'i' iiriliiiiirv iMliniatnrv ti'iii|i)'r.'itiiri'. in almut
22 il.'ivn 11 rciM>iilfl!ililr ijiiiilililv iil' -|KHii|)li(Hrs iil tin- hiirui wtTf

proiliii-cil, ( >riniiiiilly 2;{ i n* A\i\\\\\\)i tlit> wliitf imtclif.-* of tin-

fiiiiKii- wcH' |iliic»'tl in tlin cHKi'. No iiiliilt inwrt «'iM<'ri:t'il fnun tlifsc
(■()ciMiii>. SoiiH* of till- ciHiMiiK* were liiKwctfMl iil iiiti>rval.'4 and wtTt-
fiiiitjil l<> contain a lilarki-nnl or ilirty yi'llowi^h aclult. 'I'lif iii«>frti'ii
ciMcioh.-' wcrt' rc|>lar«'(l anti the Isiinn (1cvcIo|m'iI liirtlicr. I llicri nh-
lainril a lianilful of cot' ioti.« wliicli witc calofully cxaliiiiifil and wlirili
>h(iwiMl no .>ii;n!' of an infection wliati'vcr. They were divided in e(|ual
iiiiialM'rs, H(l cocoon- >ervin^ in each of the foMowinc experiment.*:

■Im'kkimi.n r A.

These soiind livinir cocoons were introduced into u lireeiliiiK chanilier
and were carefully kept free from external inl'ection from Isnrin spores.
It was sought to a.-icrtain how man\ of the cocoon- wonlil produce
liviiii: adults and those eiiier^'ins were carefully n-corded. Ten adult
larch sawflies etnerjred in the cour.se of ten days. Kleveii parasitic
in.sects were also found to emt^rjie from the cocoons; the remaindi'r
of the ciK'ooiis did not "hatcli" at all. Some of thcM- were found, on
dis.H'ction. empty. Some showed remaitis of a dead adult. Only one
co(ciiin .-howed sif;ii:< of Imirin.

I'.Xl'KHIMKNI- H.

The siame niimU'r of cocootis were useci. These were placeil
tof;(>ther with infested moss and Isnrin spores hearinj: cocoons, into a
small breeder. After 10 days (i adults and ti pura.sites were ohservnl
and were left confined in the caj;e. One of the first peculiar sym(>t(un>
ol>s<>rved in these cocoons was u darkeniiiK in colour of l(i of them.
The colour of the normal cocoons lieinj; li,i;ht chocolate, while in the>e
cases the colour was of a pronounced dull chocolate linye. Four more
adults emerged on stihsequent occa.sion.s. .\lthou;:li no sif;n> of ludrin
wei-e then noticeable on the darkening cocoon.s some of the>n were
dis.^ccted !ini| inicro.scopically < ■'"mined. Two of the e\amine<l cocoons
slMUved the interior walls lined with white fundus hyiiha'; others >howed
fuii^'al liyplue in the dead adults' body. Later on white llulTy |)atihes
occurred extprnally rather suddeidy on most of the remaining cocoons.
I'roin the appearance of tlie.-e funirous >;rowths it was evident that thev
were formed liy the Isnrln. About two months after lieirinniiiK the
experiments the fungi formed the well-known ftirked sporophores and
the inicrosccpical characters proved the fungus to be Isan'n. Spores
had be«'n produced abundantly at very early stages and no doubt had
become disseminated throughout the cage. When about thive uumtlis

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y. It. lYAI. SIM II TY Ol CWADA

altiT ^.tiirlitii.' ll'i' rxix i^ini-i.l I i>\iiiiiim'.l Ihf inli-rior of llii- ingf BRHin,
I tniin.l til.- \\\u<\<- 111.'" Mi|..Tli(iiill\ iiiid iliiniii:h..iit till' liiytT -imlilcl
with tiiH- wliiii-li . .il'.iiit- ,,t iiinv'i. 'riif-i- wi'iv i-Miiiiinftl iiiid t<miic| t..
Ik' KMiitll .i.l.mi.'^ ««f h'tna. Tlir-c <<.l"ni<'>' ii"in!iiii.-(l up to .liitr mtv
iiiiiuiK-, lull ni'MT «li!«ii|>|'«'!»r«'<l ■'^'•« '""" «"i>^'»i''lv "PI"':'"''' •"•'' "<■
pr<-.';ii 111.' iii.'-'^ i" iHMMiliaiiy r.ni.l.l«'.i all ■•vit with iniiiiitr /-in-i

,.„l,,„i..- II .loin.- hiiviiii: no hii|.|.Iv of .•.■nuciiiai I I n'tnaitii'.!

Miiall aii.l w.'iv of fours.' of .starv.MJ ap|H'araii.'<'. I ii.'\t .-.•parali-a a f.-vv
an.! traiislVrrcl tl't-tii to a ix-lii .li-li .•oiitaiiiiiiL' iiutriciii p-latini'. Il.-ri-
tJK'V iiia.li' thn-f (lays' rapid i;r..wili nii'l H" 'l.'nl" w.iuM havi' rovi-i^-.l in
till' ii-umI way till' wh. ill- siirfai'.'l.ul l..r th.' app.'arMi,.i'of u'l'latiii.' Ii.juify
inn l.a.tclia ^vliicli put a piviiianir.'.'ii.l t.i my ..l.wivali.iii. Ni'viTthclc!*".
it was prov.'.l i; ••.•atclly iliat tin- fuii^'ous npots c.msist.'.l of Isarut
f,irni„s„ ali.l 11.. olIi.T. It wa> Miipiisilin t.. IIK- that, n.'V.T tlir..U«ll«>lll
thi'sc .Api'iiiii.'nts I wa- al.l.i U< oI.s.tv.' ..iIi.t fuimi; likt- I'nunUiiiw
aiHJ .ilhi'i- .■..Million iiioiil.U. Scv.-ial inipoilant .■onclusioiis may I"-
.Iriwn fi.mi ili.-.' cxpcriiiiciil-

I. Hiaiiicl lliai 111.' .'.'.■...Ill* usc.l in i'\p«'rinn'nt> A .ui'l H wiTc ii.
cipial .■oii'liiion a- far a« llii'ir Iw'iii^' ali\i' i- c.in.'crn.'il. it i- -li.'wn from
till- uri-atiT niimlx'i of a.liills or parasites .•m.'i-uiiiL' fn>m caL'f (.'Xpcn-

mi'iit .\> all'! fr.im iIk- infi'.ti.in of a lar^c pr..p.irti f coi'o.ilis in cx-

pniiiii'iit H ihal ll' fuii'^iis Is.irio fnriniMi is liuly pai'a-iii.' on lanli
sawlly ciiii'.'li-,

_'. il i- cvi.l.'iil iliat spor.' inf('.';i.in .if tin- c.ico.nis lia.l lik.'ii
pla.'.'. •>!! no ..('casioii I ..I .serve I tlie infection of a.lults; they'll.'!
rapi ll\' I'Ut I'emain.'il iininfecti'il.

;i Til.' funt;u- /.'•■.in.i /'i/'/i.'W'i i> .'apal.le of vefietatini; saprohpy-
li.ally t'..r a ..iiiM.lt'lal.l.' leli^h of time, provi.le.l Mlllicii'lit moislui.'
is a\ ailalile The .'.'ii.lil ion- iin.ler which this mode of life was ol)serve.l
wcie el"-.' to natural .■.in.litioii>.

1 Ouim; l.i thi- saprophyti.' nuxle of lifi- there reniain.s littl.
d.iiil't tiiat the piipat ini; larva' of the larch sawfly infect themselves when
taking; to the jn'ounl U<v pupation. The rol.mies oliserve.l in the mo--
app.-are.l aliout. th.' I'li'l of .luly ami continue.l to show up to th.' .'ml "i
Seplemher, iluriiif: whi.li liiii.', of ciur-e, th.' pupation .>f th.' lar.h stwil\
takes plai'c in nature.

III.

1 ha\.' t.i reconl some -ihservatioiis on another experiment umli't-
takeli to .li.M.'Mr whether it i< po-sil'le t.i infect larch sawlly a.lult> aiii
cocoons with spor.'s oi IsonH from i>ure lulliires. Kor this piirpiw
ft Hat (rlass .lish contaiiiiii'_' Siihuiiiunn was sterilized on three successiv
(lavs in an hot air sterilizer. Althoiitrh the moss hecam.- I.r.iwn in .'oloir

(■it;«i«(iw|

I'AKAHITISM OK ISAHU KAHIMWA

M

it Htili rntniniMl HiiliKfiutorily iiii>iHt(irf» i<uliM'f|ui'iitly introdmi'il.
1 tht'ti pliicoil I niinilMT of living mlultN aixl cociMiriM in thiH H|iparutuit
uikI ihixtt'il the wlioli' with M|)(>n'!< tititt hml lH><>n |iroc|iii'i>il in a pure
niliurn of Ixtria. Tho liviiiR lulultH liixt all ilir 'tcr tliriit iiiiy« and
none iif tliow (II) (>iniT>finji; fritni tliu cofooim i. .rucUnl ihi- fiiiiKouit
ilisciifK". Aftf-r 21 (lavH iid nioit? ailultH cnitTgnl, althouK)) Vi >'<iriwn»
riMimini'd, which I ha<l cviilt-ncc to U-lipvc ('nntainc<l livinji iidiiltK. Of
tticM', nine I'vcntinilly drv('l<>|M'(l tin- lypical Isarin aiitl the nii)M al.-o
Ih-vmii to ix' I'DvtTfd with niitntTou.-i Isnria colonii'!*. 'I'lii.-* I'xpi'riniont
niiitirni* my other ol>M«rvatif)nH and ai«) indicati's that the ili«'aM«> may
1m' iirtilicially intnxhicod evi'n at hi) Into a Maff' in the din-tdopnient of
till' lari'h .lawdy. InfiM'tion takes plai'o in nature, no doubt, much
earliiT.

Although none of my experinietits were made utnler wtrictly natural
conditions; that in to r'ay in the open air, yet the oliservation that the
fun;:ui< Isnrin is repularly ff)und year after year under larrh trees, when
iiiiii' it has been fo\in'l, may indicate that the results obtained really
ilo-cly show what take> place in nature.

In conclusion, I may say that in Imiria fntinom we possess one
ccrt.iin factor, by which the increase of the Ian h sawlly may be con-
trolled. Whether it is necessary to resort to these mean^ in the face
of the every year increasing' nunitwr of in.sect parasitized larch sawlly
cticcions — is somewhat doubtful.

I ;